Heretofore, calorimeter devices have been provided which have utilized either a hot crucible such as quartz, platinum, and refractory oxides or a cold crucible such as skull melting using actively cooled copper or tungsten crucibles. However, due to contact with the container wall, crucibles often introduce contamination into the samples which influence the measured properties. Therefore, techniques which use hot crucibles are limited to non-reactive metals and alloys. Furthermore, since crucibles are more likely to interact with reactive metals and alloys at higher temperatures, calorimeters using hot crucibles are generally limited to temperatures below twelve hundred degrees centigrade. To avoid contamination at temperatures above twelve hundred degrees centigrade, cold crucibles employing various skull melting techniques have been developed but none of the techniques offer sufficient control to serve as high temperature calorimeters.
Other disadvantages of cold crucibles are the usage of large amounts of power, introduction of severe thermal gradients in the sample resulting in severe convections and possible high loss of low vapor pressure elements.
To avoid the problem of contamination, the use of electromagnetic levitators has been proposed. However, these devices also require large amounts of power and do not provide sufficient temperature control or the capability to measure the precise power absorbed by the test specimen. These devices suffer severe convection currents caused by thermalgradients and non-linear coupling and consequently high vapor losses of low vapor pressure elements.
Accordingly, an important object of the present invention is to provide high temperature calorimeter apparatus which will measure thermophysical properties of a specimen at high temperatures with accurate test control.
Yet another important object of the present invention is to provide a high temperature calorimeter in which a wide range of thermophysical properties of materials can be determined.
Still another important object of the present invention is to provide a high temperature calorimeter which is containerless and will avoid the contamination of the specimen by interaction with container walls.
Still another important object of the present invention is the provision of a high temperature calorimeter apparatus for measuring the thermophysical properties of materials at high temperatures having a low power requirement.
Yet another important object of the present invention is the provision of heating apparatus for use in a containerless high temperature calorimeter in which convection currents are reduced and in which the specimen is isothermal.